This invention relates to a control valve assembly having a plurality of control valves each including a pair of logic valves, and, more particularly to a control valve assembly for controlling a supply of hydraulic fluid to a hydraulic actuator in a hydraulic construction machine such as a hydraulic excavator.
In hydraulic construction machines such as hydraulic excavators, it has been the usual practice to use spool type directional control valves for controlling a supply of hydraulic fluid to an actuator. However, this type of directional control valves suffers the disadvantage that, since a gap for sliding portions is necessary between a spool valve body and a valve casing, internal leaks of the fluid through the gap occur when the actuator is a cylinder, thereby making it impossible to avoid an inadvertent displacement of the piston rod in the cylinder.
In view of the above disadvantage of spool type directional control valves, it has been proposed in, for example, Japanese Laid-Open Pat. No. 14670/81, to use a pair of poppet type logic valves as a control valve of the control valve assembly, with the advantage of the poppet type logic valve being that internal leaks of the fluid can be eliminated.
An object of this invention is to avoid the problems encountered in the prior art and to provide a control valve assembly comprising logic valves which enable fabrication and maintenance of a hydraulic fluid circuit to be readily effected.
Another object of the present invention is to provide a control valve assembly comprising logic valves which enables fabriction of a hydraulic fluid circuit for supplying hydraulic fluid to one actuator from a plurality of pumps in a combined flow to be readily effected.
According to the invention, a control valve assembly is provided having a plurality of control valves each including a pair of logic valves, with each of the logic valves having a pump port, a work port and a pilot port. The control valve assembly comprises a housing, and a pair of hydraulic fluid passageways arranged in side-by-side relationship in the housing. Each pair of logic valves, constituting one of the control valves, are arranged in the housing in such a manner that they are located in opposed relationship to each other in a direction substantially perpendicular to the direction in which the hydraulic fluid passageways extend. The pump ports of the pair of logic valves are in communication with the associated hydraulic fluid passageways, and the work ports of the pair of logic valves are oriented in a direction substantially perpendicular to both the direction in which said hydraulic fluid passageways extend and the direction in which said pair of logic valves are arranged.
Preferably, the pilot ports of each pair of logic valves which constitutes one of the control valves are oriented in the direction of which the pair of logic valves are arranged in such a manner that they are located at opposite ends of the logic valves from the pump ports thereof.
The control valve assembly preferably further comprises a second pair of hydraulic fluid passageways arranged in side-by-side relationship in the housing, and a second plurality of control valves each including a pair of logic valves. The second plurality of control valves are associated with the second pair of hydraulic fluid passageways in the same manner as the first mentioned plurality of control valves are associated with the first pair of hydraulic fluid passageways. The second pair of hydraulic fluid passageways are longitudinally aligned with the first mentioned pair of hydraulic fluid passageways, and the second plurality of control valves are arranged in a single row with the first mentioned plurality of control valves.
It is also possible in accordance with the present invention to provide a control valve assembly which further comprises a third pair of hydraulic fluid passageways located below the first mentioned pair of hydraulic fluid passageways, a fourth pair of hydraulic fluid passageways located below the second pair of hydraulic fluid passageways and longitudinally aligned with the third pair of hydraulic fluid passageways, and a third plurality and a fourth plurality of control valves connected to the third pair and fourth pair of hydraulic fluid passageways respectively and each control valve including a pair of logic valves. The third plurality and fourth plurality of control valves are arranged in a single row with each other whereby the row of the first plurality and second plurality of control valves and the row of the third plurality and fourth plurality of control valves provide a plurality of stages of rows of control valves. Each pair of logic valves constituting one of the third plurality and fourth plurality of control valves, have work ports which are in communication with the work ports of each pair of logic valves constituting upper ones of the first mentioned plurality of control valves and the second plurality of control valves.
The housing may comprise a single block or a plurality of block sections.